1. Field of the Invention
The invention relates to a device of the introductory portion of claim 1.
With such devices, it is possible to connect an appropriate connecting rod or a longitudinal carrier, as used in spinal column surgery, over a bone fixation element, preferably a bone screw, with the bone, in order to obtain a rigid construction.
2. Description of the Related Art
U.S. Pat. No. 4,920,959 of WITZEL ET AL. discloses an external fixator, which is relatively cumbersome. In particular, the individual clamp elements must be brought into position on the rods.
The CH-A 632658 disclose an implant for fixing bones, for which the quality of the locking in position depends directly on the prestressing force, which can be realized between the Briden body and the bone. Here also, in the event that the implant is used as a clamp, the individual elements of the clamp must be brought into position on two parallel, longitudinal rods. Accordingly, a lateral mounting is not possible. In free-hand use, particularly in percutaneous and minimally invasive use, this may be difficult to realize and represents a major disadvantage.
On the other hand, open clamps are also known from U.S. Pat. No. 5,290,288 and the WO 94/01049 A1 as well as the French patent 2775587 A1. However, these open clamps all have the disadvantage that they require an additional element for their fixation. The holding device for the clamps, that is, the bone screw, must first of all be fixed in the bone and cannot be introduced freely selectively percutaneously in order to be able to position and fix the clamp thereon only then with the bone screw. For this reason, the longitudinal carrier can be placed on the bone screw only after the clamp is positioned.
Finally, the WO95/13754 discloses a clamp, for which the longitudinal rod can be introduced laterally into the open channel of a clamp and clamped tightly there by means of a clamping screw, which can be passed through the clamp. However, the clamping screw has only this one function and is not constructed as a bone screw, which could fasten the whole construction to the bone. The same is true also for the holding device known from the DE-A 195 34 136.
The devices, known from the prior art, accordingly are quite complicated generally.